Gas-producing compositions



United States Patent GAS-PRODUCING COMPOSITIONS Kenneth Harrison. Saltcoats, and Edward Graham Cooke,

West Kilhride, Scotland, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Application November 15, 1956 Serial No. 622,498

Claims priority, application Great Britain January 27, 1956 6 Claims. (CI. 52-14) The present invention relates to improvements in or relating to compositions capable of self-sustained nondetonating gas-generating thermal decomposition comprising guanidine nitrate, ammonium nitrate and ammonium dichromate.

It is known that the inclusion of copper and many of its compounds as for example cupric oxide, copper chromite, and cuprous chloride and other cuprous and cupric salts increases the rate of gas evolution from guanidine nitrate on thermal decomposition and also has the effect of diminishing the pressure required to render such decomposition self-sustaining when a mass of the composition is merely locally heated. It is also known that amrnonium dichromate permits ammonium nitrate and guanidine nitrate to undergo self-sustained thermal decomposition even at atmospheric pressure when merely locally heated. In order to obtain higher temperatures and higher rates of burning at predetermined pressures it is often desirable to use mixtures comprising both ammonium nitrate and guanidine nitrate and to increase the catalytic effect of a chromium compound on the decomposition of the ammonium nitrate and guanidine nitrate by the inclusion of a copper compound. As the chromium compound it is usual to employ an alkali metal or ammonium salt of chromic acid. It is preferred to use ammonium dichromate because this reagent permits the burning rate of an ammonium nitrate/guanidine nitrate composition to be more easily reproducible and because ammonium dichromate is not appreciably hydroscopic. However, in compositions containing ammonium nitrate, guanidine nitrate. ammonium dichromate and the hitherto used copper compounds a slow reaction takes place between the ammonium dichromate and the copper compound during storage. This reaction affects the burning rate of such compositions and leads to their erratic behaviour and thus lack of reproducibility when they are utilised for the generation of gases.

The object of the invention is to reduce or eliminate the aforesaid lack of reproducibility in the burning rate of compositions capable of self-sustained non-detonating gas-generating thermal decomposition comprising guanidine nitrate, ammonium nitrate, a chromium compound and a copper compound.

A gas-generating composition according to the present invention comprises guanidine nitrate, ammonium nitrate, a water-soluble salt of chromic acid, preferably ammonium dichromate, and a water-insoluble cupric salt of an organic acid as for example cupric oxalate, 2CuC O,.H O; cupric citrate, 2Cu C H O .5H O; and cupric benzoate, Cl.!(C7H O )g2H 0.

It is preferred to use cupric oxalate because it contains a higher proportion of copper than cupric citrate and cupric benzoate and so less is required to increase the rate of decomposition of a composition comprising guanidine nitrate, ammonium nitrate and a water-soluble salt of chromic acid.

The burning rate of the compositions of the invention 2,923,612 Patented Feb. 2, 1960 2 may be varied by varying the proportion of cupric oxalate. cupric citrate, or cupric benzoate up to 4% reckoned on the dry weight of the composition as above this concentration little or no further variation in burning rate takes place. However, the inclusion of 4% of any one of the aforementioned cupric salts is inconveniently high as such a high percentage of the copper compound makes it necessary to lower the quantity of guanidine nitrate in order to maintain the desired oxygen value of the composition. It is thus preferred to include up to 2% of cupric oxalate. It has been found that this copper compound is effective as a catalyst when present in the composition in a concentration of as little as 0.1%, both percentages being reckoned on the dry weight of the composition.

The oxygen value of the compositions of the invention can lie between oxygen negative and oxygen balanced values and usually the relative percents of ammonium nitrate to guanidine nitrate lie between 12 to and 50 to 50.

The compositions of the invention are easily ignited and are stable and the aforementioned copper compounds have little tendency to segregate therein.

The invention is illustrated by the following examples wherein all parts are parts by weight and wherein the particle size of the guanidine nitrate is such that not less than passes through a 25 B.S. sieve and the particle size of the ammonium nitrate is such that not less than 90% passes through a 36 B.S. sieve and not more than 10% passes through a 150 B.S. sieve.

Example 1 A gas-producing composition consisting of:

is prepared by mixing the aforesaid ingredients in a blender until no blue (cupric oxalate) particles are visible, which takes about 20 minutes. The composition thus produced is compacted into pellets in a press at a pressure of 5 tons/ sq. in.

The pellets thus obtained burn at a uniform rate of 0.121 in./sec. at a pressure of 600 1b./sq. in. absolute and after storage at C. for hours burn at a uniform rate of 0.123 in./sec. at a pressure of 60 1b./sq. in. absolute (a change of 1.7%), whereas pellets produced in a similar manner from a composition wherein the cupric oxalate is replaced by cupric oxide burn at a uniform rate of 0.113 in./sec. at 600 lb./sq. in. absolute and after storage at 100 C. for 120 hours burn at a uniform rate of 0.143 in./sec. at 600 lb./sq. in. absolute (a change of 26%).

Example 2 Pellets are prepared in a similar manner as in Example 1 consisting of:

The pellets thus obtained burn at a uniform rate of 0.209 in./sec. at a pressure of 600 lb./sq. in. absolute and after storage at 100 C. for 120 hours burn at a uniform rate of 0.217 in./sec. at a pressure of 600 lb./sq. in. absolute (a change of 3.8%), whereas pellets produced in a similar manner from a composition wherein Pellets are prepared in a similar manner as in Example 1 consisting of:

Parts Guanidine nitrate 83.8 Ammonium nitrate 12 Potassium nitrate 1.2 Ammonium dichromate 3 Cupric citrate, 2c1l2C5H4O'p5H2O 2 The pellets thus obtained burn at a uniform rate of 0.080 in./sec. at a pressure of 300 lb./sq. in. absolute and after storage at 100 C. for 120 hours burn at a uniform rate of 0.077 in./sec. at a pressure of 300 1b./ sq. in. absolute (a change of 3.7%), whereas pellets produced in a similar manner from a composition wherein the cupric citrate is replaced by cupric oxide burn at a uniform rate of 0.077 in./sec. at 300 lb./sq. in. absolute and after storage at 100 C. for 120 hours burn at a uniform rate of 0.098 in./sec. at 300 lb./sq. in. obsolute (a change of 27%).

Example 4 Pellets are prepared in a similar manner as in Example 1 consisting of:

The pellets thus obtained burn at a uniform rate of 0.107 in./sec. at a pressure of 600 lb./sq. in. absolute and after storage at 100 C. for 120 hours burn at a uniform rate of 0.107 in./sec. at a pressure of 600 lb./sq. in. absolute (a change of 0.0%), whereas pellets produced in a a v '4 f similar manner from a composition wherein the cupric benzoate is replaced by cupric oxide burn at a uniform rate of 0.122 in./sec. at 600 lb./sq. in. absolute and after storage at C. for hours burn at a uniform rate of 0.145 in./sec. at 600 lb./sq. in. absolute (a change of 19%).

What we claim is:

1. A gas generating composition consisting essentially of guanidine nitrate, ammonium nitrate, a water soluble salt of chromic acid, and from 0.1 to 4% by dry weight of the total composition of a water insoluble cupric salt of an organic acid selected from the group consisting of cupric oxalate, 2-CuC O .H O; cupric citrate,

and cupric benzoate, Cu(C-,H O 2H O, wherein the oxygen value of said gas generating composition lies between oxygen negative values but sufficient to support detonation and oxygen balanced values, and wherein the relative percents of ammonium nitrate to guanidine nitrate are between 12 to 85 and 50 to 50.

2. A gas-generating composition as claimed in claim 1 wherein the water-soluble salt of chromic acid is ammonium dichromate.

3. A gas-generating composition as claimed in claim 1 wherein the water-insoluble cupric salt of an organic acid is cupric oxalate, 2CuC O .H O.

4. A gas-generating composition as claimed in claim 3 .wherein the amount of cupric oxalate is up to 2%.

5. A gas-generating composition as claimed in claim 1 wherein the water-insoluble cupric salt of an organic acid is cupric citrate, 2Cu C H O- 5H O.

6. A gas-generating composition as claimed in claim 1 wherein the water-insoluble cupric salt of an organic acid is cupric benzoate, Cu(C-,l-l O 2H O.

References Cited in the file of this patent UNITED STATES PATENTS Taylor Ian. 20, 1948 2,637,274 Taylor et al. May 5, 1953 

1. A GAS GENERATING COMPOSITION CONSISTING ESSENTIALLY OF GUANIDINE NITRATE, AMMONIUM NITRATE, A WATER SOLUBLE SALT OF CHROMIC ACID, AND FROM 0.1 TO 4% BY DRY WEIGHT OF THE TOTAL COMPOSITION OF WATER INSOLUBLE CUPRIC SALT OF AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF CUPRIC OXALATE, 2CUC2O4H2O, CUPRIC CITRATE, 